The present disclosure relates to a paper feed device which feeds sheets, an image forming apparatus and a method of controlling the paper feed device.
An image forming apparatus such as a multifunctional peripheral, a copying machine, a printer or a facsimile machine includes a paper feed device such as a sheet cassette. The paper feed device feeds out sheets which are set. The size of the sheets set in the paper feed device may be detected. In this way, it is possible to check whether or not the details of printing can be placed within the sheet. The following technology for the detection of a sheet size is known.
Specifically, a paper feed cassette device is known which includes detected means (cam group) that is provided in a cassette member, detecting means (contact type sensor) that is arranged in a cassette member fitting unit so as to be opposite the detected means, a guide frame member that is fitted to the cassette member so as to be freely moved and that guides the back edge or the side edge of stacked sheets and a coordination mechanism (a link mechanism and a transmission gear group) that is moved in a coordinated manner according to the movement of the guide frame member corresponding to the size of the stacked sheets and that moves the detected unit of the detected means away from or close to the detecting means, and which detects the size of the sheets stored in the cassette member.
The size and the remaining number of sheets which are set may be detected. For the detection, a plurality of optical sensors and a sensor such as a contact type switch are used. As the number of sensors is increased, the number of types of sheet sizes which can be detected is increased. As the number of types of sheet sizes which are detected is increased, the number of sensors which are installed is increased. In this case, the time and effort for development and the manufacturing cost are disadvantageously increased.
In order to specifically detect the remaining number of sheets, it is necessary to increase the number of sensors. However, the number of sensors installed is restricted physically and in terms of cost. At present, for example, the remaining number of sheets is detected in increments of about 25%. Hence, disadvantageously, it is impossible to accurately detect the remaining number of sheets.
In the known technology described above, a plurality of cams are used to detect the sheet size. However, the sheet sizes which can be detected are only standard sizes. The detected means and the coordination mechanism are needed. The configuration is complicated. Furthermore, in order to increase the number of sheet sizes which are detected, it is necessary to increase the number of cams. Hence, the known technology described above includes the same problem as described above. It is impossible to solve the problem described above.